Hi, Thanks for your question. As per your history concern you are on treatment for rheumatoid arthriitis. SED which means the erythrocyte sedimentation rate (ESR). SED reflects the degree of inflammation in the body. In healthy people, the ESR is low and it climbs with inflammation. It doesn t point to any particular disease, but is a general indication of the amount of inflammation in the body. In other conditionslike lupus and polymyalgia rheumatica, the ESR often correlates with disease activity. Both CRP and ESR levels are used to monitor disease activity and to monitor how well someone is responding to treatment. On medication only the inflammation will be reduced then definetly SED levels will also fall down. I hope I was able to address your query. If you have any further questions, please do not hesitate to write to me. Wishing you all the best. Thanks